Anomalous behavior of unplasticized PVC compounds in capillary flow

Capillary rheometry was performed over a temperature range of 170°–200°C and a shear-rate range of 3–3000 sec^?1 on an unplasticized poly(vinyl chloride) compound. The data were corrected for the effect of pressure on viscosity, for pressure loss in the barrel and at the capillary entrance, and for the non-Newtonian velocity profile. The pressure coefficient of viscosity was found to be in the same order of magnitude as those previously found with linear polyethylene and butadieneacrylonitrile copolymers. The pressure–shear-rate superposition of the flow curves is valid at least approximately, although the temperature–shear-rate superposition is inapplicable. The shape of flow curves at 180°, 190°, and 200°C are concave downward when they are expressed as log-shear-stress-log-shear-rate. Similar plots at 170° and 175°C, however, are very different; shear stress is independent of shear rate at low shear rates, increases somewhat and becomes independent of shear rate again at high shear rates. There is no detectable temperature dependence of flow behavior at 170° and 175°C. Irregularly shaped extrudates were obtained at higher shear rates. At constant shear rate the irregularity increased with the length of the capillary. The effect of thermal-mechanical history on the particulate and crystalline structure is discussed with possible influence on the reproducibility of the rheological data.     

Sensitivity analysis of bubble size and probe geometry on the measurements of interfacial area concentration in gas-liquid two-phase flow

Interfacial area concentration measurement is quite important in gas-liquid two-phase flow. To determine the accuracy of measurement of the interfacial area using electrical resistivity probes, numerical simulations of a passing bubble through sensors are carried out. The two-sensors method, the four-sensors method and the correlative method are tested and the effects of sensor spacing, bubble diameter and hitting angle of the bubbles on the accuracy of each measurement method are investigated. The results indicated that the two-sensors method is insensitive to the ratio between sensor spacing and bubble diameter, and hitting angle. It overestimates the interfacial area for small hitting angles while it gives a reasonable accuracy for smaller bubbles and large hitting angles. The four-sensors method gives accurate interfacial area measurements particularly for the larger bubble diameters and smaller hitting angles, while for smaller bubbles and larger hitting angles, the escape probability of bubbles through the sensors becomes large and the accuracy becomes worse. The correlative method gives an overall accuracy for interfacial area measurement. Particularly, it gives accurate measurements for larger bubbles and larger hitting angles while for smaller hitting angles, the spatial dependence of the correlation functions affects the accuracy.     

Magnetic resonance imaging of renal lymphoma with computed tomography correlation

The magnetic resonance (MR) imaging and computed tomography (CT) findings in four patients (five kidneys) with non-Hodgkin's lymphoma involving the kidneys and perirenal spaces are presented. The patterns of disease in each case were as follows: bilateral renal nodules, infiltration in the perirenal space, infiltration in the perirenal space with renal involvement, and direct invasion from contiguous retroperitoneum. On plain CT, the lesions showed slight hyperdensity (three kidneys) and isodensity (two kidneys) as compared with normal renal parenchyma. But all lesions appeared as hypodense masses with more definite margins after contrast enhancement. MR imaging findings showed iso- or slight hypointense masses on T1-weighted images and definite hypointense masses on T2-weighted images as compared with the signal intensity of the renal cortex. Dynamic imaging and conventional delayed T1-weighted imaging following Gd-DTPA injection showed no significant enhancement of the lesions. In comparison with contrast enhanced CT, despite its poorer resolution, T2-weighted MR imaging showed nearly the same accuracy in the evaluation of number and extent of the lesions without contrast medium administration. MR imaging was also useful to evaluate the patency of vessel lumen surrounded by tumor mass and to determine the location and extent of huge lesions by its multiplanar imaging capabilities.     

Gravity consolidation-sedimentation behaviors of concentrated TiO2 suspension

Consolidation-sedimentation behaviors of consolidated sediment under action of gravity were investigated using highly concentrated suspension of titanium dioxide particles under conditions of various pHs, initial heights, and initial concentrations. The average consolidation ratio of the consolidated sediment was analyzed on the basis of the simplified analytical solution obtained using the modified Terzaghi's model under the moving Lagrangian coordinate system. Although the solution pH strongly affects consolidation-sedimentation behaviors, the modified average consolidation coefficient was little influenced by the solution pH. Also, the consolidation coefficient increased in almost direct proportion to the total volume of solids per unit cross-sectional area, which changes the driving force of consolidation-sedimentation due to the overlying weight of the solid particles. The variations with time of the height of the consolidated sediment were adequately described using the analytical solution describing the average consolidation ratio with the aid of the relation that the equilibrium height was represented by a power function of the total volume of solids for a specified pH.     

Functionalized Asymmetric Linear Acenes for High‐Performance Organic Semiconductors

A series of compounds from the tetraceno[2,3‐b]thiophene and the anthra[2,3‐b]thiophene family of semiconducting molecules has been made. Specifically, synthetic routes to functionalize the parent molecules with bromo and then hexyl groups are shown. The bromo‐ and hexyl‐functionalized tetraceno[2,3‐b]thiophene and anthra[2,3‐b]thiophene were characterized in the top‐contact thin‐film transistor (TFT) geometry. They give high mobilities, ranging from 0.12 cm² V^?1 s^?1 for α‐n‐hexylanthra[2,3‐ b]thiophene to as high as 0.85 cm² V^?1 s^?1 for α‐bromotetraceno[2,3‐b]thiophene. Notably, grain size increases, going from the shorter anthra[2,3‐b]thiophene core to the longer tetraceno[2,3‐b]thiophene core, with a corresponding increase in mobility. The transition from undesirable 3D to desirable 2D thin‐film growth is explained by the increase in length of the molecule, in this case by one benzene ring, which results in an increase in intralayer interactions relative to interlayer interactions.     

Internal oxidation of dilute silver alloys

Internal oxidation of dilute silver alloys containing Al, Mg, Zn, Cu, and Sn was studied in air at temperatures between 573 K and 1173 K. Electrical resistivity, gravimetric, and gas-extraction measurements were made. The general trend of the resistivity is that it increases upon oxidation at lower temperatures and the resistivity decreases at higher temperatures in all of these alloys except Ag-Mg, in which it increases even at 1173 K. The increase in resistivity is considered to be related to the formation of clusters having excess oxygen. A detailed investigation was performed on Ag-Al alloys. The O/Al ratio in the clusters in Ag-2.2 at.% Al is much higher on oxidation at 773 K than for stoichiometric Al₂O₃ at 1173 K. The clusters release the excess oxygen on subsequent annealing at high temperatures, and decompose to stable Al₂O₃ at 1173 K.     

High resolution extreme ultraviolet spectrometer for an electron beam ion trap

An extreme ultraviolet spectrometer has been developed for spectroscopic studies of highly charged ions with an electron beam ion trap. It has a slit-less configuration with a spherical varied-line-spacing grating that provides a flat focal plane for grazing incidence light. Alternative use of two different gratings enables us to cover the wavelength range 1-25 nm. Test observations with the Tokyo electron beam ion trap demonstrate the high performance of the present spectrometer such as a resolving power of above 1000.     

Detection of fluorescence from a mixed specimen consisting of micro particles attached to different fluorescent substances using a light waveguide incorporated optical TAS

A “ubiquitous human health care system” will require a monolithic optical total analysis system (TAS) consisting of waveguides and microfluidic channels based on a transparent resin chip. Together with the rapid development of the fluorescent marking method, fluorescence analysis by TAS of mixed-microparticle specimen attached to different fluorescent substances will be necessary. Towards realization of this, we here propose a novel method for using a part of the fluorescence acquired by irradiating microparticles with AC-modulated laser power as light dedicated to the discrimination of fluorescent substances. Since the light power for discrimination was extremely weak, we extracted effective signal components using a lock-in detection method. Then, by comparison with the signal of the original fluorescence, we could determine whether the fluorescence signal was from the microparticles attached to the fluorescent substance to be discriminated. Using a mixed specimen composed of microparticle-attached fluorescent substances with emission peaks of 520 nm and 600 nm, we found that 10% of the acquired fluorescence could successfully determine the specified fluorescent substance as a discrimination signal. The peak value of the discrimination signal was approximately double the amplitude of the stationary noise in the discrimination signal.